Liberated Manuals.com -- This website is a comprehensive source of government manuals, in PDF format, free to copy, republish and distribute as you want.

PDF SB -- On this site you can read and download free books online in pdf format. It's database covers an extensive array of pdf books in different languages that describe all types of subjects and topics.

Radiomuseum.org -- Antique radios. One of the best sites overall! This site contain a countless number of photos from antique radios.

RIGPIX -- A 6.7 GB source of information and pictures of radios, accessories and more.